As a core technology of next-generation transport networks, an optical transport network (Optical transport network, OTN) has abundant operation administration and maintenance capabilities, strong tandem connection monitor capabilities, and other capabilities, and can implement flexible scheduling and management of large-capacity services.
In an OTN technology, a standard frame structure is defined to map various customer services. First, an optical channel payload unit (Optical Channel Payload Unit, OPU) overhead is added into a customer service to form an optical channel payload unit k (Optical Channel Payload Unit-k, OPUk), and then the OPUk is encapsulated, and an optical channel data unit (Optical Channel Data Unit, ODU) overhead is added into the OPUk to form an optical channel data unit k (Optical Channel Data Unit-k, ODUk), and next, an optical channel transport unit (Optical Channel Transport Unit, OTU) overhead is added into the ODUk to form an optical channel transport unit k (Optical Channel Transport Unit-k, OTUk), where k=1, 2, 3, 4, which respectively correspond to four fixed rate levels, that is, 2.5 G 10 G 40 G, and 100 G.
With the massive increase of service traffic, the optical transport network faces severe challenges. To fully utilize bandwidth resources of the OTN, technologies such as a flexible optical spectrum allocation technology, a higher-order modulation technology, and a multi-carrier technology have become mandatory technologies of the OTN. However, these technologies cannot completely satisfy actual service transmission requirements. Therefore, a requirement for evolving an OTN line rate from a fixed rate to a variable rate is increasingly urgent, that is, it is expected that the line rate is no longer limited to the foregoing four fixed rate levels, and can be changed flexibly according to an actual service traffic requirement, so as to satisfy a service bearing requirement by using an optimal bandwidth. Therefore, currently, the Study Group 15/International Telecommunication Union-Telecommunication Standardization Sector (Study Group 15/International Telecommunication Union-Telecommunication Standardization Sector SG15/ITU-T) is discussing and formulating an OTUCn signal with a flexible line rate. A bit rate of the OTUCn signal is n times of a reference rate, where n is variable. To implement a flexible line rate, dynamic adjustment of a line interface rate further needs to be studied, where the line interface rate refers to a rate of an OTU signal. However, currently, there is no technology that can dynamically adjust an OTN line interface rate.